Methods for correcting tooth movements midcourse in treatment

ABSTRACT

Appliances are made using a dental mold representing a patient&#39;s dental configuration. In particular, thermoformable plastic positioning appliances which fit over the patient&#39;s teeth may be formed over a three-dimensional mold of the patient&#39;s dentition. An apparatus and methods which employ a manipulable or reconfigurable mold to model patient dentition and gingiva at each stage of treatment. The apparatus and methods are particularly useful for performing midcourse corrections during orthodontic procedures using a plurality of such appliances in sequence.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application is a continuation of Application Ser. No. 10/087,126 (Attorney Docket No. 18563-000930/AT-00011.2), filed Feb. 28, 2002, which was a continuation of Application Ser. No. 09/779,802 (Attorney Docket No. 18563-000920/AT-000011.1), filed Feb. 7, 2001, which was a continuation of application 09/454,786 (Attorney Docket No. 18563-000910/AT 000011), filed Dec. 3, 1999, now U.S. Pat. No. 6,227,851, which claimed the benefit and priority of U.S. Provisional Patent Application No. 60/110,868 (Attorney Docket 18563-000900US/AT 00010), filed Dec. 4, 1998, the full disclosures of which are hereby incorporated by reference for all purposes.

BACKGROUND OF THE INVENTION

[0002] The present invention is related generally to the field of orthodontics. More particularly, the present invention is related to a dental model system which can be manipulated to model a series of tooth configurations for a single patient throughout orthodontic treatment.

[0003] Orthodontic treatments involve repositioning misaligned teeth and improving bite configurations for improved cosmetic appearance and dental function. Repositioning is accomplished by applying gentle controlled forces to the teeth over an extended period of time. Due to the limited space within the oral cavity and extensive movements that some teeth must undergo, the teeth will often be moved throughout a series of intermediate patterns to properly arrange the teeth. For example, molars may be temporarily distalized to create adequate space for movement of the incisors. Thus, a single patient may experience an average of 25-30 stages or alignment patterns before achieving the final desired configuration.

[0004] Such repositioning may be accomplished with a variety of orthodontic treatments and dental appliances, including conventional braces, spring retainers, positioners, and other removable aligners. With any treatment, an initial mold of the patient's teeth is made. This mold provides a model of the patient's teeth that the orthodontist uses to formulate a treatment strategy. In some instances, it may be desirable to create additional molds of the patient's teeth throughout the treatment plan to reflect individual stages. For example, the treatment strategy may be re-evaluated or a dental appliance may need to be fit to an intermediate tooth configuration.

[0005] The need for intermediate tooth configuration molds is particularly significant when using removable elastic appliances to move the teeth. Such elastic appliances typically include a thin shell of elastic material that generally conforms to the pattern of a patient's teeth, but is slightly out of alignment with the initial tooth configuration. By properly choosing the alternate configuration, placement of the elastic appliance over the teeth will move individual teeth to a desired position. Over time, multiple elastic appliances used in successive stages of treatment, will move the teeth to intermediate or final tooth positions. Such a system is described in U.S. Pat. No. 5,975,893, and in published PCT application WO 98/58596 which designates the United States and which is assigned to the assignee of the present application. Both these documents are incorporated by reference for all purposes. When using elastic appliances as described above, a series of appliances are made to reflect the successive stages of treatment. Such appliances are typically made by heating and vacuum or pressure-sealing a sheet of thermoformable plastic over the dentition of a mold.

[0006] Traditional methods of dental mold making may be utilized to fabricate a mold for such use. These methods require first forming an impression of the patent's dentition using a suitable impression material, such as alginate or polyvinylsiloxane (PVS). Plaster is then poured into the impression to create a permanent, three-dimensional mold of the dentition. To create an appliance to reflect the next desired tooth configuration in the series of treatment stages, a new mold must be created to reflect the desired configuration. This involves individually cutting the teeth from the mold and resetting the teeth in the desired configuration. Wax is then used to fill in the spaces and represent gingiva. This is a tedious process which compounds both cost and time of treatment for the patient. Resetting is accomplished by either taking into service a laboratory technician or by sending the mold out to a dental laboratory. This process typically requires 2.5 weeks to be accomplished. This represents lost time in the treatment plan as the patient cannot progress to the next stage of treatment until a positioning appliance with the new desired configuration is created. Since such an orthodontic treatment may require, for example, 25 intermediate reset molds to represent 25 stages of treatment progress, the cost and time required for such mold making may be prohibitively high.

[0007] The process of iterative mold making may be improved with the use of digital imaging and computer controlled molding systems. Here the patient's initial tooth arrangement and shape of the patient's dental arch are represented by a digital data set. The data set can then be manipulated to reflect progressive tooth arrangements. For each arrangement, the data may be used to guide computerized model fabrication systems to create a corresponding three-dimensional mold. Such techniques may speed production time and reduce costs by eliminating the need for artistic resetting of teeth in mold manufacturing.

[0008] Although the above described process aids in the production of iterative molds, further improvement may be desired. The cost in time and materials to produce each mold, though lessened, may still be significant. This cost is additive, as each new stage in treatment or each change in treatment requires the production of a new mold. Likewise, the cost of storing a series of molds for each patient throughout treatment may be formidable. In addition, it may be desirable to visualize a sequence of treatment stages, particularly in an academic environment or in a preliminary patient meeting.

[0009] For these reasons, it would be desirable to provide an alternative apparatus and methodology for realizing a series tooth configurations. Such apparatus and methods should be economical, reusable, reduce time consumption, reduce material waste, and, in particular, should reduce the need for fabricating multiple casts of teeth arrangements for stages in the orthodontic treatment. At least some of these objectives, as well as others, are met by the apparatus and methods of the invention described hereinafter.

BRIEF SUMMARY OF THE INVENTION

[0010] An improved method for repositioning teeth is provided using appliances, typically comprising polymeric shells, having cavities shaped to receive and resiliently reposition teeth. The improvement includes determining at the outset of treatment, a geometry for at least one appliance selected to move the teeth to a desired intermediate arrangement and at a later time (usually after the teeth have been moved through at least one, and usually at least two, three, four, five, or more stages) determining one or more geometries for at least one additional appliance having a geometry selected to move the teeth from an actual intermediate arrangement to a successive intermediate or final tooth arrangement. The actual intermediate tooth arrangement may be determined by any available method, usually by taking a mold and optically scanning the mold, but optionally by direct optical or other scanning of the patient's teeth.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a simplified illustration of a reconfigurable dental model system and an elastic positioning appliance fabricated with its use.

[0012]FIG. 2 is a perspective view of an embodiment of the frame of the present invention.

[0013]FIG. 3 is a flow diagram of production options for the dental model system.

[0014]FIG. 4 illustrates an embodiment of arranging the tooth members in the frame by inserting the coupling members through the ports.

[0015]FIG. 5 illustrates an embodiment of arranging the tooth members in the frame by placing the tooth members on coupling members protruding through the ports.

[0016]FIG. 6 is a simplified cut-away perspective view of the dental model system, revealing an embodiment of the manipulation devices, including View A which illustrates possible degrees of freedom in movement of each tooth member.

[0017]FIG. 7 illustrates an embodiment of manipulable simulated gingiva involving inflatable bladders.

[0018]FIG. 8 is a cut-away perspective view of an embodiment of the inflatable bladders in relation to the tooth members and frame of the dental model system.

[0019]FIG. 9 illustrates an embodiment of sub-bladders within an inflatable bladder.

[0020]FIG. 10 is a perspective view of an embodiment of manipulable simulated gingiva involving movable support shafts.

[0021]FIG. 11 is a perspective view of an embodiment of a reconfigurable dental model system comprised of movable model shafts.

[0022]FIGS. 12A and 12B illustrate an embodiment of a method of reconfiguring a dental model system involving resurfacing.

[0023]FIG. 13 is a flow diagram of a possible patient treatment method according to the principles of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention provides an apparatus and methods to produce and operate a manipulable dental model system to model a series of tooth and gingiva configurations for a single patient throughout orthodontic treatment. The tooth and gingiva configurations represent each stage of treatment from initial presentation, through intermediate stages and to the final desired configuration. The manipulable model system may be used for a variety of purposes, particularly for the production of polymeric and other elastic positioning appliances.

[0025] In one embodiment of the present invention, a single dental model system is manipulated and reconfigured to model different tooth configurations by controlling the movement of at least some of the individual tooth members, or groups of members, with manipulation mechanisms. Referring to FIG. 1, a simplified illustration of such a manipulable dental mold 100 for the fabrication of dental appliances is shown. In this illustration, the mold 100 is a positive representation of the tooth configuration and dental arch of the lower jaw. The tooth configuration is created by the placement and alignment of tooth members 101. The individual tooth members 101 are typically produced to resemble the individual shape of each of the patient's natural teeth. Although not shown, this may also include any type of dental feature, including but not limited to fillings, caps, crowns, dentures, implants, grafts, and dental appliances. In a preferred embodiment, the tooth members 101 are inserted into ports (not shown) in the frame 102 to support the configuration. It is through these ports that the tooth members may be manipulated.

[0026] Also shown in FIG. 1 is a an exemplary dental appliance, specifically an elastic positioning appliance 103, which may be produced with use of the mold 100. The appliance 103 comprises a polymeric shell 104 having an inner cavity (not shown) on the underside of the shell 104 which is shaped to receive and resiliently reposition teeth from one tooth arrangement to a successive tooth arrangement. The appliance 103 is preferably formed from a thin sheet of a suitable elastomeric polymer, such as Tru-Tain 0.03 in. thermal forming dental material (Tru-Tain Plastics, Rochester, Minn.), or Essix A-Type or Essix B-Type thermal forming material (Raintree-Essix, New Orleans, La.). The overall method for producing incremental position adjustment is provided in U.S. Pat. No. 5,975,893, previously incorporated by reference. But, in general, the shell 104 is typically produced by heating a thermoformable polymer sheet and vacuum or pressure forming the sheet over the tooth members 101 of the mold 100. Thus, the shell 104 is a direct representation of the characteristics of the mold 100. If this appliance 103 is worn by a patient as a stage in orthodontic repositioning, the shell 104 will preferably, but not necessarily, fit over all teeth or dental features supported by the patient's dental arch. Those teeth which are to be repositioned will be slightly misfit by the appliance to allow force and movement into the desired positions.

[0027] As described, the tooth members 101 are supported by a frame 102, which houses the manipulation mechanisms. A preferred embodiment of the frame 102 is depicted in FIG. 2. The frame 102 is designed to have a hollow interior portion 105 and may include a plurality of ports 106 positioned horizontally along the gingival line 107 at locations which allow for placement of the tooth members 101. The positioning of the ports 106 is meant to correspond generally to the patient's actual or desired tooth positions. The ports 106 are sized such that adequate space is available to avoid interference with the movement of the tooth members 101. Thus, the ports 106 may be oblong or elliptical, as shown, or they may form a variety of shapes, including rectangular, circular, multi-sided and/or multi-curved. Likewise, the ports 106 maybe replaced by a continuous channel or track, or the interior portion 105 may not be present, obviating the need for ports.

[0028] The tooth members 101 and frame 102 of the dental model system may be produced manually or with the use of digital imaging and computer controlled molding systems, as described previously. These production options are presented in a flowchart, FIG. 3. Regardless of the production methodology, the resulting components may then be assembled.

[0029] The tooth members 101 may be coupled to one or more manipulation devices by any of a variety of means. Referring to FIG. 4, an attachment sections 108 may be present on a bottom portion of the tooth members 101. The attachment sections 108 may be connected to coupling members 109 which may be inserted through the ports 106 for coupling to a manipulation mechanism. Alternatively, referring to FIG. 5, the coupling member 109 may be integral with the manipulation mechanism. In this case, the coupling members 109 may appear as posts or shafts protruding through the ports 106. The tooth members 101 may then be coupled to the coupling member 109 by means of an attachment section 108.

[0030] In a preferred embodiment, the ports 106 provide access to the inner portion 110 of frame 102, as shown in FIG. 6. The inner portion 110 houses one or more manipulation devices 111 which manipulate the tooth members 101. Once coupled to the manipulation devices 111, the tooth members 101 can be actuated and repositioned. The manipulation devices 111 are described in more detail below.

[0031] The simplified cut-away view of dental mold 100 shown in FIG. 6, reveals manipulation devices 111 disposed in the interior portion 110 of the frame 102. The manipulation device 111 can be a single mechanism, linked simultaneously to each individual tooth member 101 or group of members using, for example, a series of mechanical linkages or other similar means. However, as shown in FIG. 6, each tooth member 101 is preferably individually linked and controlled by a single manipulation device 111. Optionally, the tooth members 101 can be actuated by a combination of manipulation devices each providing some degree of manipulation within a given coordinate system.

[0032] To understand how tooth members 101 may be moved by a manipulation device 111, an arbitrary centerline CL is drawn through one of the tooth members 101, as seen in View A of FIG. 6. With reference to centerline CL, the tooth members 101 may be moved in the orthogonal directions represented by axes 200, 201, and 202 (where 200 is the centerline). A tooth member 101 may be translated along axes 201 and 202, or along any vector in the plane defined by these axes. Likewise, a tooth member 101 may be extruded or intruded by movement along axes 200. Torquing may be accomplished by rotation around axes 200, as represented by arrow 204. Rotation may also occur in the opposite direction than as indicated by arrow 204. Tipping or angulation may be achieved by rotation around axes 201 and 202, as represented by arrows 205 and 203 respectively. Similarly, rotation may also occur in the opposite direction than as indicated by these arrows. Thus, it is possible to perform movement of each tooth member 101 in six degrees of freedom (six DOF).

[0033] Accordingly, a practitioner can individually manipulate and arrange the tooth members 101 on the mold 100 to replicate a predetermined tooth arrangement. Each arrangement of the tooth members 101 may correspond to an incremental change in the configuration of the patient's teeth to provide a prescribed tooth movement required in each stage of an orthodontic treatment step.

[0034] The performance of six DOF movement usually requires a combination of components working individually and/or in unison to complete the various desired movements. In one exemplary embodiment, a tooth member 101 is coupled to a coupling member 109 at attachment section 108 at the bottom portion of the tooth member 101. Coupling member 109 is shown simplistically in FIG. 6 as a single member for illustrative purposes only. Since the coupling member 109 may need to provide multiple degrees of motion to tooth member 101, it may include many forms, shapes, and/or sizes. For example, certain movements may require that the coupling member 109 include one or a series of mechanical linkages, gears, springs, levers, hinges, cams, magnets and/or pneumatic pistons, used alone or in combination. The coupling member 109 couples the tooth member 101 to the manipulation device 111, also shown in a simplistic fashion merely for illustrative purposes and for generally understanding of placement.

[0035] Like the coupling member 109, the manipulation device 111 can be any single or combination of mechanical or electromechanical components that can be used to translate a driving force (electric or mechanical) into the directional movement of a member. For example, the manipulation device 111 may include a series of gears coupled to coupling member 109 and driven by a stepper motor. The motor receives a driving force, optionally from an external source, to drive the gears and incrementally rotate (i.e. arrows 203, 204, or 205) the coupling member 109, such that a degree of rotational movement is created in tooth member 101. Although, the actual mechanism used to provide the articulation of the tooth member 101 may comprise any number of interlinked components, it is likely that some of the components for providing such motion will be taken from the group comprising for example mechanical linkages, gears, springs, levers, hinges, cams, magnets and/or pneumatic pistons, used alone or in combination, as well as servos, solenoids, motors, electronics, solid state components, and the like. Alternatively, manipulation device 111 can be directly coupled to tooth member 101 without using intervening coupling member 109.

[0036] The manipulation devices 111, which create the actual six DOF movement of the tooth members 101, may be controlled manually and/or with the use of a microprocessor. In one embodiment, the repositioning of the individual tooth members 101 involves at least some of the components of manipulation device 111 being manually operated (non-computer aided). The manual controls may include, but are not limited to, knobs, screws, switches, joysticks, and other similar manual control mechanisms. In this embodiment, the practitioner will manually actuate each control mechanism, usually with finger pressure, which will in turn actuate the inner components of the manipulation device until a desired tooth arrangement is produced. Likewise, manual operation may be assisted with the visual aide of computer graphics or with instructions provided by software code.

[0037] In a preferred embodiment, the apparatus and methods of the present invention rely on the manipulation of manipulation devices 111 using a computer 300 or a workstation having a suitable graphical user interface (GUI) 301. In a specific example shown in FIG. 6, computer 300 is electrically coupled to manipulation device 111 to enable computer generated instructions to be sent to manipulation devices 111 via appropriate and well-known computer coupling methods, represented as line 302. The manipulation of tooth members 101 is driven using software appropriate for viewing and modifying the images (see above) on the GUI 301, as well as directing and controlling the tooth movements. Specific aspects of the controlling/directing software is described in detail hereinafter.

[0038] In a preferred embodiment of the present invention, the dental model system may be comprised of independently reconfigurable gingiva, in addition to tooth members, to model different tooth configurations with supporting simulated gingiva. One embodiment of reconfigurable simulated gingiva is schematically represented in FIGS. 7-9. Here, a series of inflatable bladders 400 surround each tooth member 101. As shown in FIG. 7, at least one bladder 400 is typically present to simulate the gingiva surrounding each tooth member 101. However, not depicted, each bladder 400 may simulate the gingiva surrounding more than one tooth member 101, or one continuous bladder 400 may simulate the gingiva surrounding all tooth members 101. The bladders 400 are comprised of an elastomeric material filled with air, liquid or a suitable medium. Each bladder 400 may have its own inflation port 401, leading to its own source 402. Therefore, each bladder 400 may be independently inflated and deflated by actuation of a control mechanism 411. Alternatively, the inflation ports 401 may be partially or wholly interconnected allowing manipulation of the bladders 401 with a reduced number or sources 402 or control mechanisms 411. Actuation of the control mechanism 411 may be manual or controlled by a digital processor 412.

[0039] Referring to FIG. 8, a simplified cut-away perspective view of the manipulable dental model system, reveals the possible placement of the inflatable bladders 400. The boundaries of the bladders 400 are represented by dashed lines 403. The bladders 400 may be located on the outside wall of the frame 102, which houses the attachment sections 108 and coupling members 109 which are linked to the tooth manipulation devices (not shown). Typically, the bladders 400 are covered by a continuous sheet 404 of elastomeric material to provide a smooth, consistent surface. However, the bladders 400 may alternatively be present without a cover.

[0040] Manipulation of the simulated gingiva may be further refined by a number of design features. First; each inflation bladder 400 may house a number of smaller sub-bladders 405, as shown in FIG. 9. The sub-bladders 405 may be inflated with air, liquid or a suitable medium which may or may not be the same as that which fills the main inflation bladder 400. Likewise, the sub-bladders 405 may be comprised of a material which may or may not be the same as the main inflation bladder 400. Differences in material and inflation medium may provide differing inflation dynamics. Second, each inflation bladder 400 may be comprised of a variable wall to provide differing inflation dynamics throughout the bladder 400. The wall may vary in thickness, material, amount of crosslinking of the material and number of layers, to name a few. Each variant may provide a different dynamic. For example, a portion of a bladder comprised of thin wall material will distend at a quicker rate than a portion of the bladder comprised of a thicker wall material. Thus, the simulated gingiva may be manipulated to replicate fine details of the patient's gingival configuration.

[0041] Another embodiment of reconfigurable simulated gingiva is schematically represented in FIG. 10. Here, the simulated gingiva may be comprised of a flexible sheeting 406 of any suitable material, such as nylon, silicone, latex rubber, polyurethane, woven materials or cloth. Attached to the underside of the sheeting 406 may be a series of support shafts 407. The support shafts 407 may be of any cross-sectional geometry and dimension. The support shafts 407 may be manipulated individually or in groups by control mechanisms 408, similar in concept to the manipulation devices 111 used to manipulate the tooth members 101. Like the tooth members 101, the support shafts 407 may be manipulated in up to six degrees of freedom and the control mechanisms 408 may be electrically coupled 409 to a digital processor 410 for processor control.

[0042] Additional embodiments of the present invention involve alternative designs and methods of reconfiguring a single dental model system to model different tooth and gingiva configurations. Referring to FIG. 11, a single model system may be comprised or partially comprised of a series of model shafts 500. The model shafts 500 may be of any cross-sectional geometry and dimension, and they may have any tip design. The model shafts 500 may be manipulated individually or in groups in the vertical direction by one or more control mechanisms 501, represented by boxes. Upon actuation of the mechanisms 501, the model shafts 500 may be raised to varying levels. Together, the tips 502 of the shafts 500 may form the surface features of the tooth members, gingiva and other dental features. New configurations may be created by simply altering the tip levels by manipulating the model shafts 500. The model shafts 500 may be manipulated manually by the control mechanisms 501. alternatively, the control mechanisms 408 may be electrically coupled 503 to a digital processor 504 for processor control.

[0043] Referring now to FIG. 12A and 12B, a single model system may be reconfigured to model different tooth and gingiva configurations by repeated resurfacing of the original mold. For example, as shown in FIG. 12A, it may be desirable to angulate a tooth member 101 from position A, represented by a solid line, to position B, represented by a dashed line, in the original mold. Rather than separating, angulating and recoupling the tooth member 101 to the mold, the tooth member 101 may remain in position A and be resurfaced. As shown in FIG. 12B, portions of the tooth member 101 may be removed, leaving a core 503, represented in black, in position A. A new material portion 504, represented in white, may be added to the right side to create the appearance that the tooth member 101 has moved to position B. Such resurfacing may be repeated to create different tooth and gingival configurations.

[0044] When using the reconfigurable dental mold 100 to produce a series of elastic positioning appliances 103 for orthodontic treatment, the mold 100 may be manipulated through a series of tooth configurations representing each stage in orthodontic treatment. As described previously, the initial tooth configuration is represented by the IDDS. This digital information is introduced to computer 300 for manipulation of the mold 100. The IDDS data serves as a baseline from which manipulation of the tooth members 101 begins. The Align Technology software (TREAT) described above, may be employed to determine the final tooth arrangement prescribed as the goal of the orthodontic treatment. Alternatively, the teeth may be virtually repositioned based on the visual appearance or instruction from the orthodontist. However, once the user is satisfied with the final arrangement of teeth, the final tooth arrangement is incorporated into a final digital data set (FDDS). Based on both the IDDS, FDDS, and optionally user input, a plurality of intermediate digital data sets (INTDDS's) are generated to correspond to successive intermediate tooth arrangements. The data sets are then reviewed by the orthodontist for accuracy.

[0045] In a preferred approach, the practitioner may direct the software to send an instruction to a manipulation device 111 to direct a tooth member 101 to move to a position which corresponds to a position digitally represented in the INTDDS and/or FDDS and visually represented on GUI 301. After the tooth members 101 are each manipulated and arranged to correspond to the INTDDS and/or to the FDDS data, the dental model system can be used to fabricate the system of incremental elastic positioning appliances 103 as described below.

[0046] Referring now to FIG. 13, a flow diagram is shown describing an embodiment of a patient treatment method using a manipulable dental mold 100 and elastic positioning appliances 103 according to the principles of the present invention. At the outset of the orthodontic treatment method, the reconfigurable dental mold 100 is manipulated to reflect the initial tooth and gingiva arrangement described by the first digital data set (IDDS). An elastic positioning appliance or other appliances may be produced from the mold in this configuration. The mold 100 may then be manipulated to reflect the first intermediate tooth arrangement prescribed by the first intermediate digital data set (INTDDS). At this point, an elastic positioning appliance may be produced from the manipulable mold for the first stage of treatment in the progressive alignment series. Typically, such treatment involves a series of treatment stages. For each stage, the mold is manipulated to reflect the desired intermediate tooth configuration and a positioning appliance is produced. This is repeated for each INTDDS. Finally, the mold is manipulated to reflect the final tooth configuration prescribed by the final digital data set (FDDS), from which the final positioning appliance is produced. This appliance may be worn until the patient's dental features are properly aligned in the desired final arrangement, and it may be optionally worn thereafter to retain the teeth in the desired position.

[0047] The practitioner may choose to create configurations for a sufficient number of appliances at the outset of treatment which can provide the desired treatment goals (i.e. a final tooth arrangement), thus producing an initial set of appliances. For example, the practitioner may determine configurations at the outset for at least three appliances, but most likely more. Preferably the determination of the number of configurations and appliances created is dictated by the number of stages of treatment deemed necessary by the practitioner.

[0048] However, not all configurations and appliances need to be determined at the outset of treatment. A practitioner may choose to create from one to all appliances at the outset of treatment or the practitioner may wait and produce some appliances at a later time. Furthermore, it may be necessary to make appliances again at a later time to revise a configuration to redirect the treatment. To this end, the practitioner observes the patient at each stage of the treatment, to determine if a new configuration and appliance or set of configurations and appliances are needed to re-direct the treatment to reach the final tooth arrangement. If at any time after making an observation the practitioner determines that an appliance or set of appliances are not producing the desired intermediate tooth configuration, the practitioner can further determine an actual intermediate tooth configuration that can redirect the treatment. Subsequently, the practitioner determines the configurations that follow the newly determined actual intermediate arrangement for producing additional appliances for the re-directed treatment. In particular, once the practitioner decides that an initially determined set of treatment steps and appliances is not adequate, the practitioner can determine the actual intermediate tooth configuration that has been achieved, either by taking a mold or by direct scanning of the teeth, e.g. as described in U.S. Pat. No. 5,975,893, previously incorporated herein by reference. Once the intermediate configuration is known, subsequent successive movement steps can be calculated and appropriate positioning appliances planned, also as described in U.S. Pat. No. 5,975,893. A new set of appliances can then be produced and treatment resumed. In some cases, it might be appropriate to only partially plan the treatment at the outset with the intention of making a second (and perhaps third, fourth, or more) at a time after the outset of treatment. The manipulable and reconfigurable dental model systems may optionally be used with the appliance planning protocols that rely on determining one or more actual intermediate tooth configurations during the course of a single treatment. The treatment cycle of observation of the intermediate configurations followed by either continuation to the successive configuration or modification of the treatment configuration can be repeated until the practitioner is satisfied that the final tooth arrangement has been achieved, at which time the treatment may end.

[0049] While the above is a complete description of the preferred embodiments of the invention, various alternatives, modifications, and equivalents may be used. Therefore, the above description should not be taken as limiting the scope of the invention which is defined by the appended claims. 

What is claimed is:
 1. An improved method for repositioning teeth and/or dental features using appliances having cavities shaped to receive and resiliently reposition teeth, wherein the improvement comprises determining at the outset of treatment configurations for a number of appliances sufficient to move teeth to a final arrangement and producing an initial set of appliances and at a later time determining a configuration for at least one additional appliance to move the teeth and/or dental features from an actual intermediate arrangement to a successive intermediate or final arrangement.
 2. An improved method as in claim 1, wherein the configurations for at least three appliances are determined at the outset.
 3. An improved method as in claim 1, further comprising determining that the initial set of appliances are not producing the desired intermediate arrangement and determining the actual intermediate arrangement prior to determining the configurations for the additional appliances.
 4. An improved method as in claim 3, wherein the actual intermediate arrangement is determined by taking a mold of the patient's teeth after it has been determined that the initial set of appliances is not producing the desired result.
 5. An improved method as in claim 1, wherein at least some of the appliances comprise polymeric shells.
 6. An imposed method as in claim 5, wherein at least some of the polymeric shells are thin polymeric shells. 